On Mon, Sep 26, 2022 at 04:03:06PM +1000, Alistair Popple wrote: > Since 27674ef6c73f ("mm: remove the extra ZONE_DEVICE struct page > refcount") device private pages have no longer had an extra reference > count when the page is in use. However before handing them back to the > owning device driver we add an extra reference count such that free > pages have a reference count of one. > > This makes it difficult to tell if a page is free or not because both > free and in use pages will have a non-zero refcount. Instead we should > return pages to the drivers page allocator with a zero reference count. > Kernel code can then safely use kernel functions such as > get_page_unless_zero(). > > Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx> > --- > arch/powerpc/kvm/book3s_hv_uvmem.c | 1 + > drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 1 + > drivers/gpu/drm/nouveau/nouveau_dmem.c | 1 + > lib/test_hmm.c | 1 + > mm/memremap.c | 5 ----- > mm/page_alloc.c | 6 ++++++ > 6 files changed, 10 insertions(+), 5 deletions(-) I think this is a great idea, but I'm surprised no dax stuff is touched here? Jason